Chromium Emission Research Articles

Advancing Near-Infrared Light Sources: Enhancing Chromium Emission through Cation Substitution in Ultra-Broadband Near-Infrared Phosphors.

The growing interest in the use of near-infrared (NIR) radiation for spectroscopy, optical communication, and medical applications spanning both NIR-I (700-900 nm) and NIR-II (900-1700 nm) has driven the need for new NIR light sources. NIR phosphor-converted light-emitting diodes (pc-LEDs) are expected to replace traditional lamps mainly due to their high efficiency and compact design. Broadband NIR phosphors activated by Cr3+ and Cr4+ have attracted significant research interest, offering emission across a wide range from 700 to 1700 nm. In this work, we synthesized a series of Sc2(1-x)Ga2xO3:Cr3+/4+ materials (x = 0-0.2) with broadband NIR-I (Cr3+) and NIR-II (Cr4+) emission. We observed a substantial increase in the intensity of Cr3+ (approximately 77 times) by incorporating Ga3+ ions. Additionally, our investigation revealed that energy transfer occurred between Cr3+ and Cr4+ ions. Configuration diagrams are presented to elucidate the behavior of Cr3+ and Cr4+ ions within the Sc2O3 matrix. We also observed a phase transition at a pressure of 20.2 GPa, resulting in a new unknown phase where Cr3+ luminescence exhibited a high-symmetry environment. Notably, this study presents the pressure-induced shift of NIR Cr4+ luminescence in Sc2(1-x)Ga2xO3:Cr3+/4+. The linear shifts were estimated at 83 ± 3 and 61 ± 6 cm-1/GPa before and after the phase transition. Overall, our findings shed light on the synthesis, luminescent properties, temperature, and high-pressure behavior within the Sc2(1-x)Ga2xO3:Cr3+/4+ materials. This research contributes to the understanding and potential applications of these materials in the development of efficient NIR light sources and other optical devices.

Adsorption-Reduction of Cr(VI) with Magnetic Fe-C-N Composites

In this study, the iron-based carbon composite (hereafter FCN-x, x = 0, 400, 500, and 600 calcination) was synthesized by a simple high-temperature pyrolysis method using iron-containing sludge coagulant generated from wastewater treatment settling ponds in chemical plants. The FCN-x was used for the adsorptive reduction of aqueous phase Cr(VI) effectively. The FCN-x was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), and Brunauer-Emmett-Teller theory (BET). FCN-x adsorption of Cr(VI) was examined in batch experiments using CrO42− as a function of physicochemical parameters. The chemical kinetics of Cr(VI) adsorption by FCN-500 were modeled by 1st and 2nd order empirical pseudo kinetics. Based on these experiments, FCN-500 has been selected for further studies on Cr(VI) adsorptive reduction. The maximum Cr(VI) adsorption by FCN-500 was 52.63 mg/g showing the highest removal efficiency. The Cr(VI) adsorption by the FCN-500 was quantified by the Langmuir isotherm. XPS result confirmed the reduction of Cr(VI) to Cr(III) by the FCN-500. The iron-based carbon composites have high reusability and application potential in water treatment. The electroplating wastewater with 117 mg/L Cr(VI) was treated with FCN-500, and 99.93% Cr(VI) was removed within 120 min, which is lower than the national chromium emission standard of the People’s Republic of China. This work illustrates the value-added role of sludge generated from dye chemical plants to ensure environmental sustainability.

Improving Accuracy and Sensitivity of Lanthanide-Based Luminescent Manometers by Augmented Spectral Shift Method

Luminescence manometry is most often realized by a spectral shift of luminescence bands. Typically, the shift of spectrally narrow-band emission is quantified, which is highly precise but not very sensitive to pressure variations. Alternatively, the spectral shift of a broadband emission may be exploited, which is more sensitive but less precise, due to the difficulty in accurate determination of the band centroid. In this work, a mixed approach is presented, combining the shift in broadband chromium emission from the 4T2 → 4A2 level with a narrow-band neodymium emission (4F3/2 → 4I11/2 transition), observed in the La3Ga5GeO14 spectrum. The resulting optical Nd3+-based manometer demonstrates an absolute sensitivity of 2.92 cm–1/GPa for the 4F3/2 → 4I11/2 electronic transition. An additional advantage of using this material is its negligible spectral shift with temperature, determined in the T range of 77–343 K, making the pressure readouts independent of this parameter (i.e., temperature variations).

Determination of soluble hexavalent chromium in samples of Portland cement from Brazilian cement manufacturers

Urbanization growing is nowadays highlighted in the big cities. Therefore, it is necessary to increase the production of cement, which is used in several areas of civil construction, to supplement the growing demand. Thus, the objective of this study was to determine the content of hexavalent soluble chromium in Portland cement samples from different cement industries in São Paulo state, Brazil, since this chemical species can cause adverse health effects as well as being a potential human carcinogenic for those who manipulate it. In Brazil, the emission of Cr6+ in the cement has no restrictions, since there is no current Brazilian law that determines the maximum concentration of it, whereas, in Europe, the current law 2003/53/EC establishes a maximum of 2 mg.kg-1. So, the Cr6+ content for different cement samples was determined by spectrophotometry based on the European standard EN196-10/2006. It was found by the analysis that among all types of cement produced in São Paulo, the only one that did not exceed the standard limit was the CP III, probably because this kind of cement has a high concentration of additions in its composition, responsible for diluting thereby chromium content. The other types of cement exceeded the established limit. It was concluded that Brazil urgently needs a law to regulate the hexavalent soluble chromium emission present in Portland cement to minimize the environmental and health effects that the cement out of specification may cause.

Integrating industrial source and environmental sink towards chromium emission evaluation in China: Insights from the improved substance flow analysis

The ubiquitous distributions of chromium (Cr) in environments pose threats to the health of human and ecosystem. The global output and consumption of Cr is extremely high and continuously growing, leading to cross-regional transportation and pollution via global trade. The present study identified the relationship between industrial sources and environmental sinks using the improved substance flow analysis. China, as the largest producer and consumer of Cr products, contains complete Cr related industries. Therefore, the Cr flow from Chinese eight key industrial sectors to environments in 2020 was illustrated in the research. Emission accounted for approximately 12.9%–21.8% of the flow, with the amount of 164 t in waste gas, 5.37 × 104-1.01 × 105 t in wastewater, 6.38 × 105-9.49 × 105 t in solid waste. Thereinto, ferrochromium manufacturing contributed 82.2%–85.4% to total wastes, and 1.52 × 104-2.53 × 104 t of Cr was evaluated to enter the soil accordingly. Owing to strict control for industrial wastewater and hazardous solid waste, treatment of general solid waste has become the primary pathway of Cr into the soil, contributing 77.8%–89.6%. National ferrochromium, stainless steel and refractory manufacturing contributed more effects on the soil, occupying 93.5%. Management and control of Cr in soil in China was later than other countries, such as America, Netherlands, Japan, Germany, and South Korea. However, China has issued a series of laws, regulations, action plans and standards in past decades to restrict emitter and promote industrial upgrading, which would gradually control Cr pollution and reduce the impact of industrial Cr consumption on the environment.

Enhanced NIR region emission of chromium by changing the chromium concentration in yttrium aluminum garnet (YAG) host matrix

The luminescence properties of yttrium aluminum garnet doped with variable chromium concentration were investigated under namely three different excitation wavelengths – 275 nm, 440 nm, and 580 nm. It was discerned that under 440 nm and 580 nm excitation, spin forbidden 2 E→ 4 A 2 transition shows a typical trend of increasing emission intensity with concentration increase in the range of 320–900 nm. Whereas, when the compounds with an increasing nominal dopant concentration were excited with 275 nm radiation, an exponential decrease in emission intensity of spin allowed 4 T 2 → 4 A 2 transition (in the range of 700–1000 nm) was observed. It was demonstrated that the emission of a single compound with one dopant exhibits emission in almost half of the NIR region. • Luminescence properties of YAG:Cr 3+ are investigated under 275 nm, 440 nm and 580 nm excitation wavelengths. • Material exhibits a reverse emission intensity dependence of 4 T 2 → 4 A 2 transition. • The discovery of this phenomenon might be utilized as a probe for chromium contamination in yttrium aluminum garnet.

Microdischarge in Flame as a Source-in-Source for Boosted Excitation of Optical Emission of Chromium.

A compact tandem excitation source-in-source was designed by arranging a point discharge (PD) ignited in argon/hydrogen (Ar/H2) flame and utilized for boosted excitation for the optical emission of chromium. Through a tungsten coil (W-coil) electrothermal vaporizer (ETV) located right under the tandem source without any interface for sample introduction, a miniaturized optical emission spectrometer was realized. Because the discharge gaseous atmosphere of PD was activated in the flame, the energy consumption of PD for breaking down discharge gas and maintenance of plasma was greatly saved. In addition, the flame could partially atomize or keep the atomized state of analyte atoms through its reducing environment. Therefore, the excitation capability of the tandem source was greatly improved, owing to the synergistic effect of PD microplasma and Ar/H2 flame. In addition, part of the analyte was atomized/excited on the W-coil, and thereby, dry, pure, and activated analyte species were released from the W-coil and swept into the tandem source for atomization/excitation. Through the collective effect of W-coil ETV, Ar/H2 flame, and PD microplasma, analytical sensitivity for Cr was greatly enhanced. Under the optimized conditions, with 10 μL sample solution, a limit of detection of 1.5 μg L-1 and a relative standard deviation of 3.6% (20 μg L-1, n = 5) were achieved. Its accuracy was demonstrated by successful analysis of several certified reference materials. Owing to the advantages including high sensitivity, compactness, and cost effectiveness, it is promising to facilitate the miniaturized spectrometer for more elements and potential field analytical chemistry.

Back Cover: A Near‐Infrared‐II Emissive Chromium(III) Complex (Angew. Chem. Int. Ed. 44/2021)

A strong nephelauxetic (“cloud-expanding”) effect shifts the emission of a molecular chromium(III) complex to the near-infrared-II spectral range, as reported by Claude Piguet, Oliver S. Wenger, and co-workers in their Research Article on page 23722. Image by Dr. Johannes Richers (Jo Richers Studio).

Experimental branching fractions, transition probabilities and oscillator strengths in Cr I

Branching fractions of 67 Cr I spectral lines, which covered a wavelength ranging from 213-541 nm, were measured by a high-resolution grating spectrometer which recorded the intensity of chromium emission spectrum from a hollow cathode discharge lamp. The corresponding transition probabilities and oscillator strengths were derived by the branching fractions obtained in this work combined with the radiative lifetimes reported in the previous literature.

Characterization of GAGG Doped with Extremely Low Levels of Chromium and Exhibiting Exceptional Intensity of Emission in NIR Region

Cerium and chromium co-doped gadolinium aluminum gallium garnets were prepared using sol-gel technique. These compounds potentially can be applied for NIR-LED construction, horticulture and theranostics. Additionally, magnesium and calcium ions were also incorporated into the structure. X-ray diffraction data analysis confirmed the all-cubic symmetry with an Ia-3d space group, which is appropriate for garnet-type materials. From the characterization of the luminescence properties, it was confirmed that both chromium and cerium emissions could be incorporated. Cerium luminescence was detected under 450 nm excitation, while for chromium emission, 270 nm excitation was used. The emission of chromium ions was exceptionally intense, although it was determined that these compounds are doped only by parts per million of Cr3+ ions. Typically, the emission maxima of chromium ions are located around 650–750 nm in garnet systems. However, in this case, the emission maximum for chromium is measured to be around 790 nm, caused by re-absorption of Cr3+ ions. The main observation of this study is that the switchable emission wavelength in a compound of single phase was obtained, despite the fact that doping with Cr ions was performed in ppm level, causing an intense emission in NIR region.

Waste-to-energy: Coal-like refuse derived fuel from hazardous waste and biomass mixture

This study aimed to develop Refuse Derived Fuel (RDF) with high Calorific Value (CV) from mixed hazardous wastes and biomass. The potential utilization of newly developed RDF in cement production as a fuel substitute for coal has been investigated. In this work, five types of mixed hazardous industrial wastes (rubber waste, mixed waste, paint sludge, palm oil sludge and wastewater treatment plant sludge) and three biomass types (sawdust, paddy husk and empty fruit bunch) have been used. The newly developed RDF developed in this study has a CV of approximately 18,652 kJ/kg, and its volatile matter, fixed carbon and ash content of 32 %, 40 % and 28 %, respectively. The study is revealed that substituting 5 ton/hour of RDF in the coal only emits about 301 mg/m3 of NOx, which is within the regulatory limits in Malaysia. Besides, the emission of heavy metals, including Zinc, Arsenic, Lead, Copper, Antimony, and Chromium, was also within the regulatory limits. RDF in cement manufacturing kilns is economically and environmentally attractive, as the combustion of RDF allows for a reduction of about 2.25 kg of CO2 per kg compared to coal. In terms of the efficiency of clinker and stack gas emission values, the substitution of 15 % of RDF to the coal at a feeding rate of 5 ton per hour in cement production did not cause any processing and quality issues in the existing cement production process. The result revealed that substituting 15 % of RDF with the coal in 5000 ton/day cement plant may reduce 112.8 USD/hour in operating cost. Additionally, 140 USD/hour of net saving could be achieved by saving 2.52 ton/hour of CO2 emitted from the cement production. Overall, the results concluded that RDF is a very promising resource recovery and waste treatment option for hazardous waste management.

Enhanced NIR Region Emission of Chromium by Changing the Chromium Concentration in Yttrium Aluminum Garnet (YAG) Host Matrix

Enhanced NIR Region Emission of Chromium by Changing the Chromium Concentration in Yttrium Aluminum Garnet (YAG) Host Matrix

Joining of Stainless Steel with Novel Filler Material and its Weldability Studies

Welding of Austenitic Stainless steels results in the emission of hexavalent chromium [Cr+6] fumes due to the presence of 18-22% chromium content in the stainless steel base and its filler materials. These hexavalent fumes are carcinogenic and cause respiratory problems to the welders and personnel in the vicinity of welding. In the present research work, novel Chromium free Nickel-based filler material of % wt composition 41 Ni, 8 Co, 16 Fe, 14Mo, 7 Mn, 8 Cu, 3 Nb, 1 Ti, 1 Si, 1 Al is developed and its weldability with stainless steel is studied. The microstructure and chemical composition of different metallurgical phases in the filler material and weld joints are studied using different microscopy tools and X-Ray Diffraction, respectively. The ultimate tensile strength of the filler material and weld joint welded by developed filler material is found to be 536MPa and 487 MPa, respectively. The average hardness and toughness of the filler material and welded joint are 190VHN &110J and 209VHN & 89 VHN, respectively. Results of Potentio-dynamic polarization and Inter Granular corrosion cracking (IGCC) of the weld joint has shown the corrosion rate of 1.575e-004 mils/year and 354.56 miles/year, respectively. Mechanical properties and corrosion rate of weldments welded by novel filler material are compared with that of conventional filler material. Design of experiments(DOE) using Taguchi L9 array is formulated to understand the influence of Welding current, root gap, and gas flow rate on output parameters such as Tensile Strength, Toughness, and corrosion resistance of weldment. DOE using RSM has shown maximum Tensile strength of 487Mpa, maximum Hardness of 209 VHN, and a minimum corrosion rate of 1.575e-004 mils/year has obtained with an optimum current value of 130A, 11.79 litres/min gas flow rate, and 2.33mm root gap.

Measurement of trace chromium on structural steel surface from a nuclear power plant using dual-pulse fiber-optic laser-induced breakdown spectroscopy

Remote and on-line measurement of chromium on structural steel surface in nuclear power plants is critical for protection against fluid accelerated corrosion. To improve the insufficient sensitivity of fiber-optic laser-induced breakdown spectroscopy toward trace element detection, a dual-pulse spectral enhancement system is set up. In an iron matrix, for the purpose of improving sensitivity of trace chromium analysis and reducing the self-absorption of iron, the effects of key parameters are investigated. The optimal values of the parameters are found to be: 450 ns inter-pulse delay, 700 ns gate delay, 30 mJ/6 mJ pulse energy ratio, and 19.8 mm lens-to-sample distance (corresponding to a 799 μm laser focused spot size). Compared to the single-pulse system, the shot number of dual-pulse ablation is limited for reducing surface damage. After the optimization of the dual-pulse system, the signal-to-noise ratio of the trace chromium emission line has been improved by 3.5 times in comparison with the single-pulse system, and the self-absorption coefficient of matrix iron has been significantly reduced with self-reversal eliminated. The number of detectable lines for trace elements has more than doubled thus increasing the input for spectral calibration without significantly increasing the ablation mass. Three calibration methods including internal standardization, partial least squares regression and random forest regression are employed to determine the chromium and manganese concentrations in standard samples of low alloy steel, and the limit of detection is respectively calculated as 36 and 515 ppm. The leave-one-out cross validation method is utilized to evaluate the accuracy of chromium quantification, and the concentration mapping of chromium is performed on the surface of a steel sample (16MND5) with a relative error of 0.02 wt%.

A Review of Eco-Friendly Preservative and Bio-Tannin Materials Using Powdered Barks of Local Plants for the Processing of Goatskin

Skin is a raw material which is considered as the heart of leather making process. Skin falls vulnerable upon the flayed of the animals and is seriously invaded by bacteria if it is not well protected. Curing and preservation of raw stock resist putrefaction and reserve leather quality. Worldwide, most commonly used skin preservation is by using table salt which is accused of polluting the environment by increasing soil salinity, affecting water body, releasing more than 40% dissolved solids and 55% chlorides etc. Further, on the side of leather tanning, 80-90% of all leathers is manufactured by tanning with basic chromium (III) salt, because of its excellent features and is also solemnly accused that; its safety record is cautionary, uncontrolled emission of chromium (VI) and it is a limited natural resources. Pollution control authorities of many countries are imposed severe restrictions on both salt preservation and chrome tanning forcing the tanners and researchers to look for possible alternative ways that are naturally abundant, easily obtainable, low priced, eco-friendly and offer competitive with existing tanned leather performances. The critical reviewed was targeting the recent alternatives trends to skin/hides salt preservation as well as vegetable tanning as a possible way to replace the use of basic chromium salt for the sustainability of leather industry and to further suggest another preservative and vegetable plant to be used in future studies.

Numerical study of the effects and transport mechanisms of iron vapour in tungsten inert-gas welding in argon

Tungsten inert-gas (TIG) welding uses an electric arc between a tungsten cathode and a metal anode to partially melt the anode workpiece, forming a weld pool. Metal vapour emanating from the weld pool has important effects on the arc welding process. An axisymmetric computational model of the arc and weld pool is used to examine the transport and influence of iron vapour on an argon arc plasma. In contrast to previous studies that use approximate and incomplete treatments of diffusion, the present model incorporates the combined diffusion coefficient method, which takes into account all important driving forces. The influence of metal vapour is first examined for an arc current of 400 A. Metal vapour is predicted to be present in high concentrations above the anode and near the cathode tip, and in a lower concentration in the arc column. The presence of metal vapour in the arc is found to lead to a substantial reduction in arc temperature (up to 1600 K) and current density, resulting in a significant decrease in the weld pool depth and volume. It is shown that ordinary diffusion leads to iron vapour transport upward from the anode region along the arc fringes and into the recirculating convective flow, which carries the iron vapour to the cathode region. Here the upward diffusion driven by the electric field and temperature gradient traps the iron vapour below the cathode tip, leading to a high concentration in this region. The influence of arc current is investigated in the range from 150 to 400 A. The results obtained for standard welding currents of 150, 200 and 250 A also predict significant concentrations of iron vapour in the arc, with the concentration increasing with current in the arc column and near the anode. The concentration near the cathode tip is lower at 400 A because the temperature and electric field diffusion coefficients are lower at the higher temperatures present near the cathode. Spectroscopic measurements of atomic chromium emission for argon TIG welding of a chromium anode are presented and compared to predictions of the code. The measurements show the presence of metal vapour in both the cathode and anode regions, in agreement with the model.

Numerical study of the metal vapour transport in tungsten inert-gas welding in argon for stainless steel

Metal vapour emanating from the weld pool during tungsten-inert-gas (TIG) welding affects the arc welding process. To understand the transport mechanisms of metal vapour in a TIG arc, an axisymmetric computational model is developed that includes the tungsten cathode, stainless-steel anode workpiece and the arc plasma region self-consistently. The combined diffusion coefficient method, which calculates diffusion coefficients due to mole fraction gradients (ordinary diffusion), temperature gradients, pressure gradients and the electric field is used to treat iron–chromium–argon and iron–chromium–helium plasmas. It was found that in both cases, metal vapours can reach the cathode region. The effect of different diffusion coefficients on metal vapour transport was investigated. It was found that ordinary diffusion is the main driving force for upward metal vapour diffusion away from the anode workpiece in an argon arc. The diffusive transport carries the metal vapour into the recirculating convective flow, which then transports the metal vapour to the cathode region. Here the upward diffusion driven by the temperature gradient and electric field leads to the build of high concentrations of the metal vapours adjacent to the cathode. In the helium arc, in contrast, metal vapour is transported upwards from the workpiece by electric field diffusion, which is much stronger in this case. Spectroscopic measurements of atomic chromium emission show that metal vapour can reach the cathode region in an argon TIG arc, providing support for the predictions of the model. Only by taking into account all diffusion driving forces is it possible to predict the distribution of metal vapour in a TIG welding arc.

Analysis of extreme ultraviolet spectral profiles of laser-produced Cr plasmas**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0402300) and the National Natural Science Foundation of China (Grant Nos. 11874051, 11274254, and 11564037).

Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet (EUV) region. Specifically, the EUV emission of chromium (Cr) plasmas was acquired via spatio-temporally resolved emission spectroscopy. With the aid of Cowan and flexible atomic code (FAC) structure calculations, and a comparative analysis with the simulated spectra, emission peaks in the 6.5–15.0 nm range were identified as 3p–4d, 5d and 3p–4s transition lines from Cr5+–Cr10+ ions. A normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model were assumed for the spectral simulations, and used to estimate the electron temperature and density in the plasma. The results indicate that several relatively isolated emission lines of highly charged ions would be useful for EUV wavelength calibration.

Emission reduction research and formation of hexavalent chromium in stainless steel smelting: Cooling rate and boron oxide addition effects

During the stainless steel smelting process, the control of the slag skimming process affects the formation of hexavalent chromium in the stainless-steel slag. However, the hazardous problem of hexavalent chromium in stainless-steel slag has been a major factor limiting its resource utilization. In this paper, by studying the enrichment form of chromium in stainless-steel slag and the formation mechanism of hexavalent chromium, the cooling system and the content of additives were controlled in the slag skimming process to reduce the formation of hexavalent chromium. Different means of characterization including TG-DSC, phase diagram, FT-IR, XPS, potential-pH equilibrium diagram and HJ 687-2014 method were used to characterize the presence and content change of hexavalent chromium in solid and leachate. Results showed that hexavalent chromium formation mechanism was related with the chromium diffusion in two typical Cr-containing components in stainless-steel slag. A slow cooling rate can reduce the emission of Cr(VI) in stainless-steel slag. A lower addition of boron oxide content made a lower emission of hexavalent chromium.

Paparan kromium dan kerusakan ginjal pada pekerja pelapisan logam

Chromium exposure and the kidney damage risk among electroplating workersPurposeThis study was carried out to investigate the kidney damage risk due to chromium exposure at the workplace.Method33 electroplating workers and 33 control subjects with no history of occupational exposure to chromium in Makassar were involved. Chromium levels in urine were measured with atomic absorption spectrometry. ResultsUrine from exposed workers contained higher levels of chromium, when compared with those obtained in the control group. Furthermore, there was a direct relationship was obtained between the amount of chromium and kidney damage. Kidney damage was associated with the existence of chromium level in urine. Electroplating work environments increased the high risk of chromium exposure. Workers exposed for long periods of time result in a higher level of accumulated exposure in the body. The findings of this study indicated that there was higher level of chromium exposure in electroplating workers with kidney damage.ConclusionThis study suggested the labor office to closely monitor chromium emission levels in high risk industries. Meanwhile, industry owners need to ensure that every worker uses personal protective equipment to reduce risk.